[PATCH v2 6/8] blk-throttle: Move service tree validation out of the throtl_rb_first()
From: Baolin Wang <hidden>
Date: 2020-10-08 03:52:52
Also in:
linux-block, lkml
Subsystem:
block layer, control group - block io controller (blkio), the rest · Maintainers:
Jens Axboe, Tejun Heo, Josef Bacik, Linus Torvalds
The throtl_schedule_next_dispatch() will validate if the service queue is empty before calling update_min_dispatch_time(), and the update_min_dispatch_time() will call throtl_rb_first(), which will validate service queue again. Thus we can move the service queue validation out of the throtl_rb_first() to remove the redundant validation in the fast path. Signed-off-by: Baolin Wang <baolin.wang-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> --- block/blk-throttle.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f1bcb5c..38aed8b 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c@@ -638,9 +638,6 @@ static void throtl_pd_free(struct blkg_policy_data *pd) throtl_rb_first(struct throtl_service_queue *parent_sq) { struct rb_node *n; - /* Service tree is empty */ - if (!parent_sq->nr_pending) - return NULL; n = rb_first_cached(&parent_sq->pending_tree); WARN_ON_ONCE(!n);
@@ -1224,9 +1221,13 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) unsigned int nr_disp = 0; while (1) { - struct throtl_grp *tg = throtl_rb_first(parent_sq); + struct throtl_grp *tg; struct throtl_service_queue *sq; + if (!parent_sq->nr_pending) + break; + + tg = throtl_rb_first(parent_sq); if (!tg) break;
--
1.8.3.1